Preheat the grill.

Place the beer in a saucepan and bring the liquid to a boil over medium heat. Add the sausages and cook for 10 minutes. Remove from the sausages from the liquid, reserving the liquid. Set the sausages aside.

In a large saute pan, over medium heat, render the bacon until crispy, about 6 to 8 minutes. Remove the bacon and set aside. Discard the all the bacon fat except for 1/4 cup. Place 1/4 cup of the fat back into the pan and add the onions. Season with black pepper. Saute for 2 to 3 minutes, or until tender. Add the cabbage. Season with salt and pepper. Continue to saute for 4 minutes or until the cabbage is tender. Stir in the garlic, mustard and 2 cups of the liquid from the sausages. Bring the liquid to a simmer and cook for 8 to 10 minutes, stirring occasionally. Reseason with salt and pepper. Place the sausages on the grill and cook for 2 minutes on each side, or until nicely marked. To serve, place the sausages between each bun. Top each sausage with some of the smothered cabbage. Serve with the potato salad.